3) REMARKS ON THE FIGURES OF PLATE II. 
sion that the simple rule of plus and minus is that which 
renders them different one to the other. Fig. A” plus the 
element 0, equals fig. C” plus that same element 0, and 
fig. A” or fig. C’ or D” minus the element 4, equals the 
fig. B” which is minus the very same element 0. 
Any of these figs. A” B’C” or D” minus certain ele- 
ments would render them equal to fig. H”, and if rendered 
still further minus would equate them with figs. F’F’ F’”; 
consequently fig. F” plus those very same elements would 
establish it equal to either D’”C”B” or A”, and this rule is 
productive of the idea that the plus quantity A” equals the 
plus quantities C” and D”, and is the archetype of B’E” 
and I” the minus quantities, whereupon it must be con- 
cluded that B’E” and F” are minus quantities of their own 
archetypes which fully equalled D”, or C”, or A.” 
We should not forget that those elements which persist 
for the archetype, and which render it plus, are identical 
with those elements which fail for the minus vertebral 
figure, and which render it thus minus or various. 
The subtraction of an element from a whole or plus 
quantity renders it now various to what it once was. 
When 34 is subtracted or omitted from A”, this is a varia- 
tion from plus to minus. When equal quantities, such as 
the elements marked a,d,c, are subtracted from plus 
homologues, such as figs. AYA” A”, then the remainders 
are equal and still homologous to each other, although 
various to plus quantity. When, again, the like auto- 
genous elements a, 0, c, are subtracted from figs. C’C’C”, 
the same condition of variety occurs. This remark applies 
also to figs. D’D’” D”. 
When a part is subtracted from a whole, such as part 4 
from fig. A”, we are enabled (even without having seen 
the operation of subtraction actually performed) to ascer- 
tain by comparative rule how much quantity is lost to 
fig. A”. For, when we compare fig. A” minus 4, to an- 
other cervical vertebra plus 4, we then create the idea of 
the element 4 for the minus vertebra, and the like remark 
may be made respecting figs. C’ and D”, these figures 
containing elementary parts identical with those of fig. 
A”. Hence, therefore, if figs, A” or C” or D”, deprived 
of the element 4, will invariably create the idea of that 
quantity of which they are minus when compared to figs. 
A”, C’, or D”, where the same quantity 0 persists, so 
will fig. B’, which is now minus the element 4, create the 
idea of this lost quantity when fig. B” shall be compared 
to any form which contains 4 in the same spinal series. 
The subtraction of equal quantities from equal figures 
will leave the remainders equal to one another. If the 
element 4 be withdrawn from figs. A”, C’; and D”, the 
remainders of those figures will be equals. But if unequal 
quantities be subtracted from originally equal figures, then 
the remainders of those figures will be unequal, and thus 
it is that figs. E” and F” are unequal or various to each 
other, and ‘to figs. A” B’C” or D”, which latter would also 
result as unequal quantities, if unequal quantities had been 
subtracted from them. 
A comparison of plus and minus quantities which hold 
a serial order, such as figs. A” B’C” D’” BE’ EF”, will not fail 
to suggest the idea that they are only various to each 
other as unequal quantities, and this idea we believe to be 
inseparable from the one, namely, that they are thus 
created by reason of the fact that unequal quantities have 
been subtracted from archetype equals or plus forms, such 
as figs. A”C” or D”. 
It is certain that plus quantities, such as figs. A”C”D”, 
are equals containing homologous elements. It is also 
certain that those forms contain proportionals severally 
equal to figs. B” HE” F”, and it is moreover certain that if 
any anatomist chose to assert that B’ HE” and EF” were 
unequal quantities proportioned from such as A” C”D”, 
there could not be found in all the science of mathematics 
a single rule in denial of such imterpretation. Hence, 
when we see that the simple subtraction of elementary 
quantity is sufficient to establish inequality or variety 
amongst serial forms, and also that the minus figure such 
as it is for B’ E” or F”, is still homologous to some quantity 
in either A” C’ or D”, then the interpretation defends 
itself under shelter of the following rule, viz.: “ We must 
take care to admit no more causes of natural things than 
what are true and sufficient to explain their phenomena.” 
“We must observe always to assign the same causes for 
the same natural effects.” ** The subtraction of quantity 
is sufficient to explain the variety which distinguishes figs. 
EF’ HE” and B” from one another, and from figs. A”C” and 
D”, and the same cause will always produce the same 
effects. Nature is simple in her operations, and never 
luxuriates in superfluous causes of things. The skeleton 
axis 1s ike a geometrical series of proportional quantities, 
which decrease from the quantity a+ 4 to a—4, and thus 
we have figure A” commencing series compared with fig. 
F”’, which terminates it. 
* Regule Philosophandi. Newton’s Principia. 
